The present invention relates to the field of drilling in the ground, in particular for the purpose of constructing foundations, such as for example continuous screens made up of juxtaposed concrete wall elements.
The invention relates more precisely to a drilling machine for excavating in the ground in a drilling direction that is substantially vertical, and more particularly in hard soil.
The invention relates more particularly to a machine comprising:
an anchor module having at least one anchor element for preventing the anchor module from moving relative to the walls of the excavation in the drilling direction, the anchor module having a substantially vertical longitudinal direction;
a drilling module provided with cutter members, the drilling module being movable relative to the anchor module in the drilling direction; and
a movement device arranged between the anchor module and the drilling module in order to move the drilling module relative to the anchor module in the drilling direction.
This type of drilling machine is generally used for drilling in hard ground, e.g. in granite. The movement device serves to exert additional thrust on the drilling tools, for the purpose of facilitating excavation.
Such a machine is described in particular in EP 0 811 724. It can be understood that the anchor module serves to hold the drilling machine stationary in the excavation.
In that machine, the movement device, constituted by jacks, supports the weight of the drilling module while the machine is suspended, i.e. while it is not in contact with the ground for drilling. This applies in particular while the drilling machine is being moved, e.g. in order to be taken to the zone for drilling, or indeed while it is being extracted from the excavation after the drilling operation.
The drilling module is particularly heavy when it has motor-driven cutter members, hydraulic circuits, and the pump member. It can thus be understood that the jacks need to support a weight that is very large when the drilling machine is suspended, which might damage them.